Chronic pain is defined as a painful condition that lasts longer than 3 months. 1 Chronic pain can also be defined as pain that persists beyond the reasonable time for an injury to heal or a month beyond the usual course of an acute disease. There are four basic types of chronic pain: (1) pain persisting beyond the normal healing time for a disease or injury, (2) pain related to a chronic degenerative disease or persistent neurologic condition, (3) cancer-related pain, (4) pain that emerges or persists without an identifiable cause. Chronic pain differs from acute pain in its function. Acute pain is an essential biologic signal to warn the individual to stop a potentially injurious activity or to prompt one to seek medical care. Chronic pain serves no obvious biologic function. Chronic pain patients presenting to the emergency department (ED) have not been well studied, despite their apparent numbers.

Complete eradication of pain is not a reasonable end point in most cases. Rather, the goal of therapy is pain reduction and return to functional status. Chronic pain syndromes discussed in this chapter include myofascial headaches, "transformed" migraine headaches, fibromyalgia, myofascial chest pain, back pain, complex regional pain types I and II, postherpetic neuralgia, and phantom limb pain. Drug-seeking patients are also covered.

If you are suffering from headaches, you can make the pain stop just by following some basic but little known principles. Take 15 minutes browsing through this guide and you'll find dozens of tips to gain control in the battle against headache pain.